For the past years, a number of adjustable positioning mechanism have been developed for positioning an optical assembly relatively to another.
For example, U.S. Pat. Nos. 4,753,510 and 4,889,406, both issued to Sezerman, describe an adjustable optical connection between two optical fibers. The preferred embodiment disclosed in these patents is an optical assembly fixed within a flange. By using fine pitch screws, such a flange may be connected and then adjusted relatively to a fixed member, which may be another flange containing another optical assembly. A resilient member, which is disposed between the plates, acts as a spring load during the tilt adjustment. One problem associated with such configuration is that the tilt axes are not fixed during the adjustment, since the resilient member is allowed to deform randomly. Therefore, in addition to a rotation of the mobile flange from the reference plate, undesirable and uncontrolled displacement in the other degrees of freedom may occur. Sezerman solved this problem in describing an alternate embodiment using a solid fulcrum instead of a resilient material. In this configuration, the adjustment screws circumferentially spaced would provide a controlled rotation around a fix and solid point. This mechanism would basically work as a “ball and socket” type of joint. This system, having 3 or more adjustment screws, requires the simultaneous operation of 2 or more screws to pivot the assembly about an axis. This complexifies the alignment procedure of the mechanism and makes it less intuitive to use. Another feature of the Sezerman mechanism is that it has to get resilient material inserted between the screws and the mobile member. That causes the assembly to be non-stabilized. It is understood that the assembly position equilibrium is dependent on the counterbalance of the load in the resilient material and the load in the metallic parts, such as the screws and the fulcrum. External forces applied on the optical components aligned by this mechanism will therefore likely result in misalignment of the system. Furthermore, given that the mechanical properties of the resilient material can and will likely change in time, this may also lead to changes in the equilibrium conditions and misalignment of the mechanism. This problem is also present in the preferred embodiments described in Sezerman patents. Another aspect of these inventions is that although they provide compact adjustment mechanisms, they are not readily suited to provide for hermetic attachment of the adjusted optical component to a wall or optoelectronic package such as those used for telecommunication systems.
U.S. Pat. No. 5,095,517 issued to Monguzzi and al. proposed an optical connector with a housing receiving a movable component having a spherically shaped surface portion in which the optical element is inserted. The spherical surface of the mobile element is in contact with a mating surface on the fixed member and allows rotation. Once the optimal position is achieved, tightening elements are used to create and maintain enough friction force on the spherical joint to lock the mobile part and prevent further rotation. The assembly therefore do not rely on resilient materials to maintain its position. However, the position is still not rigidly locked and external forces of sufficient magnitude can counterbalance the friction force and misalign the mechanism. Furthermore, the proposed connector does not contain its own alignment mechanism such as alignment screws and therefore such assembly requires external manipulators to be aligned and cannot be used in a stand alone configuration.
The invention developed by Dallakian and shown in U.S. Pat. No. 6,198,580 relates to an optical mount using a spherical bearing surface. The mechanism uses 2 independent and perpendicular adjustment pivots. The mobile part and the fixed element are mated and maintained together using spring tensionners. The assembly is then tilted by tightening or loosening the adjustment screws and the equilibrium of the assembly is created by balancing the tension load in the springs and the compression load in the screws. Given that no locking mechanism is featured in this system, the alignment of the optical mount can easily be modified by external forces and therefore this invention is confined to laboratory use only and cannot be assigned to be part of an optoelectronic module.
Therefore, there is still a need for an adjustable positioning mechanism overcoming the disadvantages of the devices discussed above. Moreover, it would be desirable to provide an adjustable positioning mechanism easily manufacturable for a commercial use, that can be compact, easily adjusted, rigidly locked in place, and that prevents any movement that could occur from spring fatigue and/or resilient material or the influence of an external force while providing potential hermetic sealing.